My guess is you have something holding the brakes, or the brakes are not actually off. Are you sure you are pressing the foot brakes, turning the park brake off, then releasing the footbrakes, confirming they are released by checking their position, then trying to use the tow?
I have tested this, and checked with some other people running the TBM, and they are having no problems.
Even aerox, in the above post, seems to be having no problems.